Seems Kilby acquired/peddled Whitworth steel tubes in tubesets:

http://www.doublegunshop.com/forums/ubbthreads.php?ubb=showflat&Number=130190&page=1

http://www.doublegunshop.com/forums/ubbt...true#Post230400
Matska - Whitworth 20390 - with the Sauer 21887 makes one wonder to whom the number belonged. Was T. Kilby the Whitworth raw tube source?

Feodor Osipovitch Matska peddled his offerings till circa 1907 so a tubeset with Whitworth #19595 would have been prior to that so a sporting weapon with a Whitworth number in the 24k range would be in your date range estimation.

Curious why C. Modé picked them up in singles.

Kind Regards,

Raimey
rse